<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        body {
            margin: 0;
        }

        header {
            height: 160px;
            position: relative;
            overflow: hidden;
            --percentage: 0.5;
        }

        header .view,
        header .tree {
            position: absolute;
            top: 0;
            right: 0;
            bottom: 0;
            left: 0;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        header img,
        header video {
            position: absolute;
            display: block;
            width: 120%;
            height: 100%;
            object-fit: cover;
        }

        header .morning {
            z-index: 20;
            opacity: calc(1 - (var(--percentage) - 0.25) / 0.25);
        }

        header .afternoon {
            z-index: 10;
            opacity: calc(1 - (var(--percentage) - 0.5) / 0.5);
        }

        header .view {
            transform: translatex(calc(var(--percentage) * 100px));
        }

        header .tree {
            transform: translatex(calc(var(--percentage) * 50px));
            filter: blur(3px);
        }

        header .view,
        header .tree,
        header .morning,
        header .afternoon {
            transition: .2s all ease-in;
        }

        header.moving .view,
        header.moving .tree,
        header.moving .morning,
        header.moving .afternoon {
            transition: none;
        }

        header .window-cover {
            opacity: calc((var(--percentage) - 0.9) / 0.1);
        }
    </style>
</head>

<body>
    <header>
        <div class="view">
            <img src="https://assets.codepen.io/2002878/bilibili-winter-view-1.jpg" class="morning" alt="">
            <img src="https://assets.codepen.io/2002878/bilibili-winter-view-2.jpg" class="afternoon" alt="">
            <video autoplay loop muted class="evening">
                <source src="https://assets.codepen.io/2002878/bilibili-winter-view-3.webm" type="video/webm" />
            </video>
            <img src="https://assets.codepen.io/2002878/bilibili-winter-view-3-snow.png" class="window-cover" alt="">
        </div>

        <div class="tree">
            <img src="https://assets.codepen.io/2002878/bilibili-winter-tree-1.png" class="morning" alt="">
            <img src="https://assets.codepen.io/2002878/bilibili-winter-tree-2.png" class="afternoon" alt="">
            <img src="https://assets.codepen.io/2002878/bilibili-winter-tree-3.png" class="evening" alt="">
        </div>
    </header>
    <script>
        let startingPoint
        const header = document.querySelector('header')

        header.addEventListener('mouseenter', (e) => {
            startingPoint = e.clientX
            header.classList.add('moving')
        })

        header.addEventListener('mouseout', (e) => {
            header.classList.remove('moving')
            header.style.setProperty('--percentage', 0.5)
        })

        header.addEventListener('mousemove', (e) => {
            let percentage = (e.clientX - startingPoint) / window.outerWidth + 0.5

            header.style.setProperty('--percentage', percentage)
        })
    </script>
</body>

</html>